CancerCancer

• What is Cancer?– Cancer develops when cells in a part of the body begin to

grow out of control. Although there are many kinds of cancer, they all start because of out-of-control growth of abnormal cells.

– Normal body cells grow, divide, and die in an orderly fashion. During the early years of a person's life, normal cells divide more rapidly until the person becomes an adult. After that, cells in most parts of the body divide only to replace worn-out or dying cells and to repair injuries.

– Because cancer cells continue to grow and divide, they are different from normal cells. Instead of dying, they outlive normal cells and continue to form new abnormal cells.

– Cancer cells develop because of damage to DNA. This substance is in every cell and directs all its activities. Most of the time when DNA becomes damaged the body is able to repair it. In cancer cells, the damaged DNA is not repaired. People can inherit damaged DNA, which accounts for inherited cancers. Many times though, a person’s DNA becomes damaged by exposure to something in the environment, like smoking.

• Source - ACS

• Male Cancer Death RatesMale Cancer Death Rates

Cancer Death Rates, for WomenCancer Death Rates, for Women

*Age-adjusted to the 2000 US standard population.Source: US Mortality Public Use Data Tapes 1960-2000, US Mortality Volumes 1930-1959,National Center for Health Statistics, Centers for Disease Control and Prevention, 2003.

0

20

40

60

80

100

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

Lung

Colon & rectum

Uterus

Stomach

Breast

Ovary

Pancreas

Rate Per 100,000

Lifetime Probability of Developing Cancer, Lifetime Probability of Developing Cancer, Men, US, 1998-2000Men, US, 1998-2000

Source: DevCan: Probability of Developing or Dying of Cancer Software, Version 5.1 Statistical Research and Applications Branch, NCI, 2003. http://srab.cancer.gov/devcan

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CanceCancerr

• What is the molecular basis of cancer?What is the molecular basis of cancer?– Cancer is a Cancer is a genegenetic disease.tic disease.

•Mutations in genes result in altered proteins– During cell division– External agents– Random event

•Most cancers result from mutations in somatic cells

•Some cancers are caused by mutations in germline cells

• Theories of cancer genesisTheories of cancer genesis– Standard Dogma

• Proto-oncogenes (Ras – melanoma)• Tumor suppressor genes (p53 – various cancers)

– Modified Dogma• Mutation in a DNA repair gene leads to the

accumulation of unrepaired mutations (Loeb, 1974) (xeroderma pigmentosum)

– Early-Instability Theory• Master genes required for adequate cell reproduction

are disabled, resulting in aneuploidy (Philadelphia chromosome)

• Problem posingProblem posing– Can we understand the mechanism(s) of

cancer by examining the expression patterns of genes in the cancer cell?

– Can we use gene expression patterns to determine the properties of a cancer?

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